In a major leap forward for individuals with limb amputations, a novel surgical method has been developed to enable a more natural walking ability. Reported by MIT News, researchers from MIT and Brigham and Women’s Hospital have pioneered an approach that provides patients with enhanced neural feedback from their residual limbs, allowing for more natural and obstacle-free movement.
The typical robotic prosthetics on the market, while advanced, have not been able to offer the full neural control that the body's own nervous system can. These devices usually employ a combination of sensors and predefined algorithms to mimic natural gait patterns. What the MIT team has managed to do is, effectively reconnect muscles within the residual limb, which in turn make it possible to quite directly control a prosthetic leg, delivering a significant upgrade in proprioceptive feedback, which is the awareness of where one's limb is in space.
Hugh Herr, a professor at MIT and the brain behind this study, explained the significance of the breakthrough. "No one has been able to show this level of brain control that produces a natural gait, where the human’s nervous system is controlling the movement, not a robotic control algorithm," Herr told MIT News. This development could herald a new era of autonomy for amputees, who have traditionally had to cope with less-responsive artificial limbs that respond to a very limited extent to their body's signals.
The technique used in the process is termed the agonist-antagonist myoneural interface (AMI), which involves preserving the dynamic interaction between muscle pairs that usually gets severed during standard amputations. By maintaining this interaction after the surgery, patients can experience a range of movement and proprioception similar to that of their natural limb. This innovative surgery has been performed on around 60 patients worldwide, with promising results. "Because of the AMI neuroprosthetic interface, we were able to boost that neural signaling, preserving as much as we could," said Hyungeun Song, a postdoc in MIT’s Media Lab and lead author of the study published in Nature Medicine, as reported by MIT News.
Comparative testing between individuals with traditional amputations and those who had undergone the AMI surgery revealed striking improvements. The group with the AMI-linked prosthesis displayed enhanced coordination, power, and speed similar to that of non-amputees, even though the sensory feedback they received was less than 20% of what an intact limb would typically transmit. "A small increase in neural feedback from your amputated limb can restore significant bionic neural controllability, to a point where you allow people to directly neurally control the speed of walking, adapt to different terrain, and avoid obstacles," explained Song to MIT News.
Collaboration has been key to the success of this transformative research, with notable contributions from Matthew Carty, a surgeon at Brigham and Women’s Hospital and an associate professor at Harvard Medical College. Carty reinforces the potential impact of this work: "This work represents yet another step in us demonstrating what is possible in terms of restoring function in patients who suffer from severe limb injury," according to MIT News. Funded by the MIT K. Lisa Yang Center for Bionics and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, this project pushes the boundaries of what's achievable in patient care and prosthetic technology.
